Fixing Device Substrate Width Variation for Temperature Uniformity

The patent applies local quality by positioning the temperature sensing element at a specific location on the substrate where the long side edges are linear, rather than uniformly across the entire substrate. This localized placement ensures the sensing element measures temperature only in the uniform region, avoiding the non-uniform areas caused by edge irregularities. The substrate itself has varying thermal properties across different regions, with the central region having better thermal uniformity than the edge regions.

The patent segments the substrate into different functional regions: a central region with linear long side edges where temperature sensing occurs, and edge regions where non-linearity exists. By dividing the substrate into these distinct zones and placing the temperature sensing element only in the appropriate central region, the system achieves accurate temperature measurement while avoiding the harmful effects of edge non-uniformity.

Instead of requiring the entire substrate including edges to have perfectly linear long side edges, the patent applies local quality by only requiring linearity in the specific region where temperature sensing occurs. The edge regions can have manufacturing variations without affecting temperature control accuracy, as long as the central sensing region maintains linear edges for uniform heat transfer.

The patent extracts the temperature sensing function from the edge regions and places it only in the central region with linear edges. This separation allows the edge regions to have manufacturing tolerances without compromising temperature control, while the central region maintains the necessary precision for uniform heat transfer and accurate sensing.